Do I need substrate heating cables?

Hi. I've started buying all the needed supplies for setting up a 70g
planted aquarium. The only item I have not yet decided on is heating
cables for the substrate. Do I really need these? I've bought
flourite for a substrate, live in central FL, the house temperature
hovers around 78-81 in the summer but in the winter we open the
windows a lot so the temperature might be more in the low-mid
seventies. Will the cables be effective at these temperatures?

If you think they are needed, do you recommend any in particular?

Thanks in advance.